Bi73–: The Missing Family Member, Finally Isolated and Characterized

The synthesis and structure of Bi73–, the only missing member of the family of heptanuclear pnictogen cluster anions Pn73– (Pn = pnictogen, a group 15 element excluding the unique nitrogen), is reported. The new species is synthesized by oxidation of a solution of K5Bi4 by the solvent pyridine in the presence of (C6H6)­Cr­(CO)3. The existence of the species in solution is confirmed by electrospray mass spectrometry, while its structure is elucidated by single-crystal X-ray diffraction in the compound [K­(2,2,2-crypt)]3Bi7·2py (monoclinic, P21/n, a = 13.8739(13) Å, b = 24.878(2) Å, c = 26.401(2) Å, β = 96.353(4)°, V = 9056.5(14) Å3, Z = 4, and R1/wR2 = 0.0636/0.1390 for the observed data and 0.0901/0.1541 for all data).